This invention relates to a needle selection control apparatus for a circular pattern knitting machine, and more particularly to an improved control apparatus which controls the timing of selection of a series of needles mounted on a needle cylinder of an electronic circular pattern knitting machine by supplying to needle selector means of the circular knitting machine input pulse signals produced by sensor means in synchronism with moving cylinder needle and whose phases have angles of lead controlled by the control apparatus in accordance with the increasing number of revolutions of the circular knitting machine.
Electronic circular knitting machines are capable of knitting articles of various patterns at very high speeds, and have hereto been used for industrial mass production purposes. It is known that circular knitting machines of this type have a needle cylinder including a series of knitting needles arranged at regular intervals thereon for axial sliding movement, and needle selector means which selects needles according to desired knitting patterns during high-speed rotation of the needle cylinder and controls the movement of selected needles in axial direction between a knit or operation position for engaging the selected needles with knitting thread and a welt or inoperative position. The known needle selector means includes an electromagnetic actuator which operates to select cylinder needles during the high-speed rotation of the cylinder, and has several different types.
For example, circular knitting machines have a needle cylinder diameter of 760 mm on which a series of about 2,100 needles are mounted and arranged at an extremely small pitch of about 1 mm. A very high performance needle selector means is therefore required so that the selection of needles arranged at such a small pitch and rotating at very high speeds may be carried out within an extremely short period of time and with great accuracy. In a well-known circular pattern knitting machine, cylinder needles are moved at high speeds equivalent to a frequency of several hundred cycles per second. The needle selector means provided in circular knitting machines must meet the need of selecting cylinder needles within a very extremely short time and with great accuracy, and therefore have limitations to the speed at which the machine should be rotated and its knitting capability. The needle selector means also has its performance greatly limited or influenced by the ability of its actuator to respond to input pulse signals within a very short time. As far as circular knitting machines are hereto known, none have such actuators as can satisfy this requirement sufficiently. An actuator is operated upon receipt of input pulse signals to move jacks to a knit position or a welt position for engagement or disengagement with cylinder needles, and in practice an actuator requires a time of a given length for responding to such signals. This time becomes a very important factor which limits the speed of the needle cylinder. Different types of actuators are known, one of which is an actuator which biases jacks to be associated with needles toward the knit position or welt position by mechanically engaging the head of a plunger which is electromagnetically actuated for axial movement, with the jacks. Another known actuator has an electromagnetic solenoid actuated to bias the jacks for movement between the knit and welt positions. Those two actuators have been improved in all aspects, but still have limitations to their response time to which there could be expected no further improvement. It will readily be understood from the above that the circular knitting machine has its speed of rotation limited or influenced by the capability of the needle selector means. The known selector means is not satisfactory in this respect.
The present invention has the above facts in view, is based on the observation that the known circular knitting machine has an actuator whose rise time contains an idle or inactive time, and has overcome the disadvantages above described. With the known circular knitting machine, the actuator has an idle or inactive time of a fixed duration regardless of the number of revolutions of the needle cylinder, which adversely affects the working property or capability of the needle selector means particularly when the needle cylinder is rotating at very high speeds.
The present invention provides an apparatus for controlling the needle selector means for selectively placing cylinder needles in position, and which improves the working property of the needle selector means by eliminating the idle or inactive time earlier mentioned. The elimination of the idle time is carried out by providing input pulse signals of advanced phase for the needle selector means.